There are roughly two states subject to radio resource control (“RRC”) state management of terminals according to 3GPP UMTS System Release 1999 or equivalent, which has been standardized (see Non-Patent Document 1). These two states are two RRC states, namely “RRC connected mode” and “RRC idle mode.” The RRC connected mode is further divided into the following four states, namely “CELL_DCH,” “CELL_FACH,” “CELL_PCH” and “URA_PCH.”
CELL_DCH refers to a state in which a terminal and a base station are connected via a dedicated channel, and significant power is consumed in this state since transmission and reception are carried out constantly. Furthermore, since a dedicated channel is set up, a large amount of data can be communicated. Moreover, the transfer control is a network control. That is to say, when a measurement report is received from the terminal, a cell switch command is issued from the network.
CELL_FACH refers to a state in which a terminal and a base station communicate via a shared channel, and less power is consumed in this state than in CELL_DCH since transmission and reception are carried out only when necessary. Furthermore, since a plurality of terminals communicate within a limit of a shared channel, CELL_FACH is not appropriate for communicating a large amount of data. Furthermore, the transfer control is a terminal control. That is to say, when a terminal moves from one cell to another, it is necessary to change its state to CELL_DCH or CELL_FACH and perform a new cell registration (i.e. cell update).
CELL_PCH refers to a state in which a terminal waits for new data to be generated or a call from a base station, and no data is communicated in this state. Furthermore, setting information and so on for earlier services is retained. Furthermore, in the case of transfer within a cell, CELL_PCH assumes a waiting state at discontinuous receiving intervals (i.e. DRX: discontinuous reception), in which no data is communicated and little power is consumed. Moreover, the transfer control is a terminal control. That is to say, when a terminal moves from one cell to another, it is necessary to change its state to CELL_DCH or CELL_FACH and perform a new cell registration (i.e. cell update).
URA_PCH refers to a state in which a terminal waits for new data to be generated or a call from a base station, and no data is communicated in this state. Furthermore, setting information and so on for earlier services is retained. Furthermore, in the case of transfer within a UTRAN registration area (“URA”: i.e. a plurality of cell groups), URA_PCH assumes a waiting state, in which no data is communicated and little power is consumed. Moreover, the transfer control is a terminal control. That is to say, when a terminal moves from one URA to another, it is necessary to change its state to CELL_DCH or CELL_FACH and perform a new URA registration (i.e. URA update).
Next, the RRC idle mode refers to a state in which a terminal waits for new data to be generated or a call from a base station, and no data is communicated in this state. Furthermore, setting information and so on for earlier services is not retained. Furthermore, in the case of transfer within a routing area (“RA”) or location area (“LA”) (i.e. a plurality of cell groups), the RRC idle mode assumes a waiting state, in which no data is communicated and little power is consumed. Moreover, the transfer control is a terminal control. That is to say, when a terminal moves from one RA to another, it is necessary to change its state to CELL_DCH or CELL_FACH and perform a new RA registration (i.e. RA update).
FIG. 1 shows a conceptual diagram of these RRC states and state transitions. The network side makes a terminal transition to an RRC state suitable to the condition of the terminal according to the state transitions shown in FIG. 1, thereby reducing the power consumption of the terminal and realizing effective use of radio resources.
However, this system has the following major problems. First, given that there are many states and controlling both terminals and the network is complicated. Second, given that a state transition is started by an RRC message and the transition takes time, it is difficult to make transitions more frequently.
Therefore, studies are underway for efficient terminal state management in long term evolution (“LTE”)/system architecture evolution (“SAE”), which is standardized by the 3GPP, and the inclusion of only the following two states is anticipated (see Non-Patent Document 2).
In the RRC connected mode, data is communicated between a terminal and a base station using a shared channel and a control channel is used to use the shared channel. Furthermore, if there is no data, power consumption is reduced by employing discontinuous reception (i.e. DRX: Discontinuous Reception) and discontinuous transmission (i.e. DTX: Discontinuous Transmission). Furthermore, the volume of data communication is controlled through shared channel resource allocation. Furthermore, the transfer control is a network control. That is to say, when a measurement report is received from the terminal, a cell switch command is issued from the network.
On the other hand, the RRC idle mode refers to a state in which a terminal waits for new data to be generated or a call from a base station and in which therefore no data is communicated. Furthermore, setting information and so on for earlier services is not retained. Furthermore, in the case of a transfer within a tracking area) (i.e. “TA”: a plurality of cell groups), the RRC idle mode assumes a waiting state, in which no data is communicated and little power is consumed. Moreover, the transfer control is a terminal control. That is to say, when a terminal moves from one TA to another, it is necessary to change its state to RRC connected mode and perform new TA registration (i.e. TA update).
In this way, unlike the above-described UMTS, in LTE/SAE, it is necessary to perform the transfer control through a network control for terminals in a DRX/DTX state.
Non-Patent Document 1: 3GPP, TS25.331, 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, Radio Resource Control (RRC), Protocol Specification.
Non-Patent Document 2: 3GPP, TS25.813, 3rd Generation Partnership Project, Technical Specification Group Radio Access Network, Evolved Universal Terrestrial Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN), Radio interface protocol aspects.